When we design a building, we generally don’t think about how perfect the wall section should be. Most architects think of how perfect or sexy the building should be. Maybe some think about how it should function.

Thanks to Louis Sullivan, “form follows function” provides the basis for a discussion. The function of the wall is to keep the building dry. Therefore, if the exterior wall keeps us warm and dry, that is all we really need to consider when designing these beautiful pieces of architecture. Why should we care about the materials that make up the wall?

We really do need to put thought into the wall composition because the wall needs to breathe. Air carries water vapor that can cause damage to the interior components of the wall if it can’t breathe. Addressing this concern requires that we focus on ensuring air movement through the wall.

Joseph Lstiburek, a principal at the Building Science Corporation, has been writing about how to make a perfect wall for at least 10 years. He usually writes a column in the ASHRAE Journal on topics related to exterior wall design. Last November he wrote about the perfect wall: “Joseph Haydn Does the Perfect Wall.” His article makes it seem pretty simple to design a perfect wall or roof. With a brick wall, an insulated metal panel system, or a standing-seam roof panel, it is all about controlling the water, air, and vapor. A perfect wall is one in which the vapor or air inside the wall can evaporate in any climate. In “The Perfect Wall,” an article Lstiburek wrote in 2008, he posited that the only thing architects need to change is the amount of insulation we specify.

With that being said, it is important to refer your state energy code when it comes to new construction. The 2015 iteration of the New Jersey Energy Code, for instance, contains some major changes regarding the amount of insulation required for new construction. This is good. It will help conserve the use of fossil fuels. Wall construction does play a very important function on the road to achieving sustainability.

Suzanne Sowinski is the founder and director of sustainable building at Sowinski Sullivan Architects, PC. She received her master’s degree in sustainable design over ten years ago. As a registered architect, she believes that the practice of architecture and the teaching of sustainable design are equally important in the 21st century.